                                                  :query-params params
                                                  :throw-entire-message? true}))
       {:status 400
-       :headers {"Content-Type" "application/json"}
+       :headers json-header
        :body (generate-string validation-results)})))
 
 (defn get-exercise-solution

                           (-> construct
                               (dissoc :lang)
                               (set/rename-keys {:construct :value})))]
    (generate-string (map format-construct sparql-constructs))))

(defroutes api-routes
  (context "/api" []

            [cheshire.core :refer [generate-string]]
            [clojure.set :as set]))

(def ^:private json-header
  {"Content-Type" "application/json"})

(defn sparql-query
  "Execute a SPARQL query in an HTTP GET request using `params` and HTTP `headers`."
  [{:keys [query]
